Dozens of people, including Murdoch protégé Rebekah Brooks and Andy Coulson, a former adviser to prime Minister David Cameron, already have been arrested and several have been charged with phone hacking and related crimes.

Police say Wednesday's arrests are part of a separate conspiracy to hack phones, primarily from 2005 to 2006, at the News of the World.

Brooks and Coulson are both former News of the World editors. Brooks later became chief executive of News International, a UK subsidiary of Murdoch's News Corp. empire. Coulson went on to become Cameron's director of communications before resigning early in 2011.

The hacking scandal prompted Cameron to set up an independent, judge-led inquiry -- named for Lord Justice Leveson, its chairman -- to make recommendations on journalistic ethics and examine the relationship of the press with the public, police and politicians.